1. Field of the Invention
The present invention relates to a display device. More particularly, the present invention relates to a liquid crystal display panel (LCD panel).
2. Description of Related Art
In recent years, the performance of thin film transistor liquid crystal displays (TFT-LCDs) is developing towards high contrast ratio, no grayscale inversion, little color shift, high brightness, deep color, high color saturation, fast response, and wide viewing angle.
At present, many techniques can achieve the wide viewing angle, which includes the twist nematic (TN) liquid crystal plus wide viewing film, the in-plane switching (IPS) LCD panel, the fringe field switching (FFS) LCD panel, and the multi-domain vertically alignment (MVA) LCD panel and so on.
For example, the MVA LCD panel has a plurality of strip slits formed on pixel electrodes, and a plurality of strip protrusions arranged on a color filter array substrate. The combination of the slits and the protrusions makes liquid crystal molecules in a liquid crystal layer to be inclined in different directions, so as to achieve a wide viewing angle.
FIG. 1 is the partial cross-sectional view of a conventional MVA LCD panel. Referring to FIG. 1, the conventional MVA LCD panel 100 includes an active device array substrate 110, an opposite substrate 120, and a liquid crystal layer 130. The active device array substrate 110 has a plurality of pixels 140 arranged in an array on the substrate. Each of the pixels 140 has an active device 150 and a pixel electrode 160 electrically connected to the active device 150. In addition, the opposite substrate 120 includes plural sets of R, G, B color filters and a common electrode 170. The liquid crystal layer 130 is disposed between the active device array substrate 110 and the opposite substrate 120.
As shown in FIG. 1, in order to increase the viewing angle of the MVA LCD panel 100, a plurality of strip slits 162 is usually formed in the pixel electrodes 160, and a plurality of protrusions 172 is usually disposed on the opposite substrate 120. Thus, the electric field distribution between the strip slits 162 and the strip protrusions 172 makes the liquid crystal molecules in the liquid crystal layer 130 to be inclined in different directions, thereby increasing the viewing angle of the MVA LCD panel 100.
In addition, Fujitsu has discussed on the response time of the MVA LCD panels in Society for Information Display (SID) in 2001, and proposed information related to brightness of the MVA LCD panels. The pixels and brightness of MVA LCD panels proposed by Fujitsu will be described as follows.
FIG. 2A is a top view of a part of the pixels of a conventional MVA LCD panel. As shown in FIG. 2A, a protrusion 172 is disposed above a pixel electrode 160. FIG. 2B shows a result of the optical simulation in a bright state of FIG. 2A. As shown in FIG. 2B, distinct dark areas appear near the protrusions 172 at the central part and on two sides of FIG. 2B, so the overall brightness of the MVA LCD panel cannot be further improved.
Furthermore, the fabrication of the protrusion 172 requires an additional photolithography and etching process (PEP), which increases the manufacturing cost. Moreover, liquid crystal molecules around the protrusion 172 are liable to be influenced by the protrusion 172 to assume an inclined arrangement, and thus the light leakage of MVA LCD panel easily occurs in the dark state, resulting in the decrease of the contrast.